Device for thermally treating substrates

ABSTRACT

The aim of the invention is to enable substrates to be thermally treated in a more homogeneous manner. In order to achieve this, a device is provided for thermally treating substrates, especially semiconductor wafers, comprising at least two adjacent, essentially parallel heating elements which respectively have at least one heating wire. The two adjacent heating elements are embodied in such a way that they are quasi-complementary, at least in parts, in terms of the coiled and uncoiled segments of the heating wires pertaining thereto.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for the thermal treatmentof substrates, especially semiconductor wafers, with at least twoadjacent heating elements that are disposed essentially parallel to oneanother and are each provided with a heating filament. The apparatus isin particular related to a rapid heating unit in which the substratesare subjected to rapid temperature changes.

In the semiconductor industry, it is known to thermally treat wafersduring the process of manufacturing the same. For this purpose,generally so-called rapid heating units are utilized, such as aredescribed, for example, in DE-A-19952017, which originates from the sameapplicant. These units include a reactor having lamps for heating thesubstrates (preferably only one substrate is disposed within thereactor), and generally, although not necessarily, a process chamber(preferably of quartz glass) that is transparent for the lamp radiationand that is disposed within the reactor and surrounds the substrate. Thesubstrate is subjected via the lamp radiation within the reactor or theprocess chamber to a thermal treatment pursuant to a predefinedtemperature-time-curve in a defined process gas atmosphere or in avacuum. For the process result of the thermal treatment, it is veryimportant that the wafer be heated uniformly, and that a homogeneoustemperature distribution result on the wafer surface, or that apredefined temperature distribution can be realized as well as possible.Deviations from a homogeneous temperature distribution over thesubstrate are especially advantageous for silicon wafers if the processtemperatures exceed 1200° C. and the heating and cooling rates aregreater than 50° C./s. Under these process conditions, it has been shownthat in the region of the final temperature an approximately parabolictemperature distribution having a temperature difference of about 5 to20° C. (as a function of the diameter of the wafer) over the waferdiameter provides the best process results with regard to freedom ofslip. However, such uses with desired, defined non-homogeneoustemperature distribution over the wafer or the substrate are more theexception, since these processes entail the greatest demands on theregulatability and the temperature measurement of the substratetemperature, which only the most modern plants today can fulfill.

Primarily during the heating and cooling phases, there occurs withdisc-shaped wafers the problem of very non-homogeneous temperaturedistributions, especially in the edge region of the wafer, which cannotbe controlled or can be controlled only inadequately. Thus, the edge ofthe wafer heats much more significantly and rapidly during the heatingphase than does the inner portion of the wafer. This more rapidheating-up is due to the fact that at the edge of the wafer, a largerouter surface per volume of wafer is provided than in the interior ofthe wafer. Via this additional outer surface, the edge of the waferabsorbs more of the heat radiation than does the interior of the wafer(edge effect). Furthermore, the edge of the wafer is irradiated by alarger wall surface of the reactor, essentially via reflection ofradiation, and “shadows” the interior of the wafer. Due to the reactorwalls, the edge region of the wafer is thus irradiated that much moreintensely the higher is the reflectivity of the wall surfaces. Thus,during heating-up of the wafer, the edge of the wafer, in addition tothe pure “edge effect”, is additionally heated due to the presence ofthe reactor walls. Since the reactor walls of rapid heating units areusually cooled (cold wall reactors), and the wall temperature isgenerally less than 100° C., the reactor walls have a relatively lowthermal inherent or characteristic radiation relative to the reflectedradiation, as a result of which the influence thereof during usualprocess temperatures of greater than 400° C. can be disregarded.

On the other hand, during the cooling phases the wafer cools morerapidly at the edge of the wafer than in the interior of the wafer,since via the larger surface per wafer volume at the edge, more thermalradiation is emitted. In addition, surfaces of the reactor chamber thatare disposed across from the substrate and are generally arrangedparallel to the substrate reflect the radiation energy given off fromthe wafer back to the center of the wafer in a reinforced manner,thereby further slowing down the already slow cooling-off of the centerof the wafer. This slowing down is that much greater the more reflectiveare the surfaces, or the more these surfaces radiate thermal energy. Theinfluence of the edge of the wafer and of the process chamber walls uponthe homogeneity of the temperature is also designated as thephoton-box-effect, and is, among other things, essentially a result ofthe reflection of a portion of the heat radiation at the reflectivechamber walls, and is included in the main problems during the rapidheating of semiconductor substrates, especially if during the entireduration of the process, in other words also during the dynamic phasesof the heating-up and cooling-off, an as uniform as possible or apredefined temperature distribution (which itself can again be afunction of the temperature) is to be achieved over the wafer.

From the aforementioned DE-A-19952017 it is known to surround the waferwith a compensation ring in order to reduce the photon-box-effect. Inparticular, the compensation ring is tilted as a function of theprogress of the process in order to achieve a shadow effect relative tothe lamps at the edge of the wafer. In addition to this approach, it isalso known to provide light-transforming plates, also knows ashot-liners, parallel to the wafer in order to indirectly heat the wafervia such plates, and hence to reduce the photon-box-effect. However,these approaches can only partially reduce the photon-box-effect, andthey lead to a complicated construction of the rapid heating unit.

In the known rapid heating units, rod-shaped tungsten-halogen heatinglamps are generally utilized. The heating lamps are provided with atungsten filament that is kept in a halogen-containing atmosphere.During the operation of the lamps, tungsten from the filament isvolatilized and reacts with gas molecules to form tungsten halide.During the operation of the lamps below approximately 250° C., acondensation of the tungsten on the lamp tubes can occur, which,however, can be avoided if the lamp glass is kept in a temperature rangebetween 250° C. and 1400° C. The condensation should be avoided, since afog connected therewith on the glass adversely affects the heatingprocess and the service life of the lamps. If the tungsten halide comesinto the vicinity of the filament, sufficient thermal energy is appliedto break the chemical bond and to again deposit the tungsten upon thefilament. Subsequently, the halogen gas can repeat the process. Thiscycle is known as the halogen process.

With the conventional rod-shaped tungsten-halogen lamps, the filamentextends approximately in the center of the lamp cross-section along thelongitudinal axis of the lamp, and is uniformly spirally coiledessentially over the entire length of the lamp. Only in the end regionsare linear filament sections provided for the transition into therespective lamp socket. As a result, an essentially uniform heatingcapacity can be achieved over the entire length of the lamp, which,however, contributes to the aforementioned photon-box-effect since, asmentioned above, with a uniform heating capacity over the surface of thewafer the edge region is heated more pronounced than is the centralregion.

With the aforementioned DE-A-19952017 the wafer that is to be treated isfurthermore disposed in a process chamber that comprises quartz glass,whereby the heating lamps are disposed outside of the process chamber.The quartz glass is transparent for the radiation emitted from theheating lamps. After a heating of the wafer within the process chamber,the wafer emits a short wave thermal radiation in the range of 0.3 to 4μm, as well as a longer wave thermal radiation in the infrared range ofgreater than 4 μm. The quartz glass of the process chamber is notentirely transparent for this longer wave thermal radiation of greaterthan 4 μm, and therefore a large portion of this thermal radiation isabsorbed by the quartz glass. Thermal radiation that is not absorbed isreflected back to the chamber, and again a large portion is absorbed inthe quartz glass. A remainder falls on the wafer and is absorbedthereby. Due to the absorption of the thermal radiation in the quartzglass, there is a localized heating-up of the process chamber,especially in a region of the process chamber that is disposed directlyabove or below the wafer. This effect is further reinforced by areflection of the thermal radiation at the reflective chamber walls ofthe unit, since the thermal radiation is essentially reflected directlyback to the wafer, so that a region of the process chamber thatessentially corresponds to the projected shape (i.e. having the samecircumferential shape) of the substrate is heated significantly morethan regions disposed beyond this region. This process again reinforcesthe so-called photon-box-effect, especially if the process chamber isgreatly heated up, so that it irradiates back to the wafer within thechamber. This return radiation prevents a rapid cooling of the wafer,especially in the middle of the wafer. The process chamber of quartzacts as a sort of energy trap for the long wave thermal radiation,whereby due to a coupling between wafer and process chamber the centralregion of the wafer is always irradiated more strongly, since theprocess chamber walls that are disposed approximately across from thisregion are at a higher temperature than are the other process chamberwalls. This makes it clear that a non-homogeneous temperaturedistribution of the process chamber (e.g. of quartz) has an influenceupon the temperature distribution of the wafer. For this reason, it isattempted to cool the process chamber as homogeneously as possible.However, the process chamber temperatures can readily reach a range of600° C.

Proceeding from the aforementioned state of the art, the object of thepresent invention is to provide an apparatus for the thermal treatmentof substrates, especially semiconductor wafers, that enables a morehomogeneous or defined heating of the substrate that is to be treated.

SUMMARY OF THE INVENTION

Pursuant to the present invention, this object is realized with anapparatus for the thermal treatment of substrates, especiallysemiconductor wafers, having at least two adjacent heating elements thatare disposed essentially parallel to one another and are each providedwith a heating filament, wherein the two adjacent heating elements, atleast in part, are embodied approximately complementary to one anotherwith respect to the coiled and uncoiled sections of their heatingfilament.

The complementary configuration of the heating filaments of the twoadjacent heating elements means that at least one coiled section of thefilament of a heating element is disposed entirely or at least partiallyin the region of an uncoiled section of the heating filament of theadjacent heating element. Conversely, an uncoiled section of the heatingfilament of a heating element can be disposed entirely or at leastpartially in the region of a coiled section of the heating filament ofthe adjacent heating element.

By providing uncoiled and coiled sections of at least two adjacentheating elements that are disposed approximately parallel to oneanother, whereby the sections are embodied approximately complementaryto one another, it is possible to achieve over the surface of the wafer,especially along the filaments, differently controllable radiationintensities, which can be used to reduce the photon-box-effect. Theirradiation characteristics of the filaments of the at least two heatingelements can be adapted to the temperature conditions that exist in oron the wafer by appropriate activation with electrical power. Mechanicaladditional elements, such as, for example, a compensation ring or ahot-liner, for reducing the photon-box-effect, can be eliminated.

The present invention advantageously offers the possibility, with anappropriate arrangement of the adjacent heating elements, for the latterto heat the wafer in such a way as if it was being irradiated from asingle heating element, i.e. as if only a single heating filament werepresent that, however, due to the approximately complementary sectionsis controllable with respect to its irradiation intensity if theindividual heating elements are individually electrically activated.This considerably broadens the ability to regulate in comparison toprevious rapid heating units having rod-shaped lamps without having toreduce the previous power features of the units, since the units can atany time be operated in such a way as if they were equipped withconventional rod lamps.

The filament of a heating element preferably has n coiled sections and muncoiled sections, whereas the filament of the adjacent heating elementhas m coiled and n uncoiled sections, whereby n and m are respectivelyintegers. This enables a complimentary arrangement of coiled anduncoiled sections of adjacent heating elements. The coiled sections ofthe one filament of a heating element are preferably respectivelydisposed at least partially in the region of the uncoiled sections ofthe filament of the adjacent heating element. In so doing, the coiledsections of the filaments can overlap at most 30% of their sectionallength or 10% of the diameter of the substrate that is to be treated. Inthe same manner, the uncoiled sections of filaments preferably overlapat most 10% of the diameter of the substrate that is to be treated. Oneembodiment of the invention can also have no overlapping of thecorrespondingly complimentarily embodied sections. The degree of overlapdepends upon how close to one another the filaments that arecomplimentarily embodied relative to one another are, and whatrequirements are prescribed relative to the permissible deviations ofthe desired temperature distribution upon the wafer.

Pursuant to a preferred embodiment of the invention, the filaments aresymmetrical relative to a plane of symmetry that centrally intersectsthe longitudinal axis of the filaments and is perpendicular thereto,with this being done to obtain a symmetry that is adapted to thesubstrate. Preferably, respectively at least two adjacent inventiveheating elements are associated with one another on at least one sideand form a group. In this connection, the heating elements of a groupare preferably provided with a common socket in order to hold thegrouped heating elements in a defined position relative to one another.The heating elements of a group can advantageously be individuallyelectrically activated in order in this manner to be able to control thespatial irradiation profile along the axis of the heating elements ofthe group. Furthermore, the individual groups can similarly beindividually electrically activated in order to be able to also controlthe irradiation profile of the groups in the direction of the extensionof the groups. The groups are advantageously disposed approximatelyparallel to one another and parallel to a plane that is advantageously asurface of the wafer. By appropriate activation of the groups and theheating elements within a group, the possibility is provided, not onlyin the longitudinal direction of the heating elements but also in thedirection perpendicular thereto, of controlling or regulating theintensity of the irradiated power. In this way, it is possible togenerate different irradiation profiles over the surface of thesubstrate. The respective filaments advantageously have a constantelectrical resistance per unit of length in order over the length of thecoiled section of the filament to produce a constant irradiationintensity. Deviations herefrom can also be advantageous, especially thedensity and/or type of coiling of the coiled sections can benon-homogeneous.

At least one heating element advantageously has at least two chambersfor accommodating the filament, and in particular a plurality ofchambers that are separated from one another for accommodating differentsections of the filaments. By providing different chambers, the halogenprocess can be optimally established in the respective chambers,especially taking into consideration the respective filament section.Especially in the region of the uncoiled sections of the filaments thereexists the danger of condensation of the tungsten on the lamp tube,since in the region of the uncoiled sections there is a lesser heatingthan in the region of the coiled sections. For a good control of thehalogen process as a function of the different sections, a differentpressure and/or a different gas is provided in at least two of thechambers.

To achieve a homogeneous temperature distribution upon the surface ofthe substrate, the filament of a heating element preferably has acentrally disposed, coiled section with adjoining uncoiled sections,whereas the filament of the adjacent heating element has a correspondinguncoiled central section and two adjacent coiled sections. As a resultof this arrangement, a different heating-up of the edge regions of thesubstrate relative to the central region is made possible in order tocounteract the aforementioned photon-box-effect. In this connection, thecoiled central section of the one filament preferably has a length ofapproximately ⅘ of the diameter of the substrate that is to be treated.The coiled sections that are adjacent to a central, uncoiled sectionpreferably have a length of approximately ⅓ of the diameter of thesubstrate that is to be treated.

For a good and uniform heating-up of the substrates, the heatingelements are preferably rod lamps, the filaments of which deviate fromthe longitudinal axis of the lamps by less than one millimeter.

The object of the invention is realized with an apparatus for thethermal treatment of substrates, especially disc-shaped semiconductorsubstrates, which apparatus has a housing that forms an oven chamber, atleast one radiation source within the oven chamber, and a processchamber for accommodating the substrate that is to be treated, wherebythe process chamber is essentially transparent for the radiation of theradiation source, and whereby the housing has inner walls that arereflective for the radiation, in that at least one inner wall of thehousing, which is disposed approximately parallel to a plane of thesubstrate that is to be treated, has at least two zones having differentreflection characteristics, whereby at least one zone essentiallycorresponds to the projected shape of the substrate. By providing thedifferent reflection characteristics, a local heating-up of the processchamber, which is caused by thermal radiation that is emitted from thesubstrate and that is partially absorbed by the process chamber andreflected at the inner walls of the housing, can be reduced. Due to thefact that one zone essentially corresponds to the projected shape of thesubstrate, a local heating-up of the process chamber directly above thesubstrate, especially in a region that essentially corresponds to theprojected shape of the substrate, can be reduced.

Preferably, the light incident in one zone is reflected in anessentially diffused manner, as a result of which a uniform distributionresults within the oven chamber of the thermal radiation that is emittedfrom the substrate and is reflected in the one zone. To achieve thiseffect, the zone of the inner wall is preferably blasted with sand orabrasive, or is roughened by some other chemical, electrochemical, ormechanical process.

Pursuant to one embodiment of the invention, the one inner wall has ashape that is different from the projected shape of the substrate, forexample having a quadratic shape in comparison to a round substrateshape. The one zone preferably corresponds essentially to the size ofthe substrate.

The object of the present invention is also realized with an apparatusfor the thermal treatment of substrates, especially disc-shapedsemiconductor substrates, which apparatus has a housing that forms anoven chamber, at least one radiation source within the oven chamber, anda process chamber for accommodating the substrate that is to be treated,wherein the process chamber is essentially transparent for the radiationof the radiation source, in that at least one wall of the processchamber that is disposed essentially parallel to a plane of thesubstrate that is to be treated is provided with at least two zoneshaving different optical characteristics, whereby one zoneadvantageously essentially corresponds to the projected shape of thesubstrate. In this way, localized heating of the process chamber wallabove and below the substrate due to the thermal radiation given offfrom the substrate can be reduced, and hence an overheating of thecentral portion of the substrate can be counteracted.

Pursuant to one embodiment of the invention, the one zone is essentiallytransparent for the thermal radiation given off by the substrate inorder in this manner to avoid a local heating-up especially in thisregion. In this connection, the one wall of the process chamberpreferably has a shape that is different from the projected shape of thesubstrate, and the one zone corresponds essentially to the size of thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described subsequently in greater detail with theaid of preferred embodiments with reference to the drawings; shown inthe drawings are:

FIG. 1 a schematic cross-sectional view from the front through a rapidheating unit;

FIG. 2 a schematic cross-sectional view from the side through a rapidheating unit;

FIG. 3 a schematic cross-sectional view through a rapid heating unit,whereby lamps pursuant to the present invention are shown in an upperbank of lamps;

FIG. 4 a schematic view of a lamp group pursuant to the presentinvention;

FIG. 5 a schematic cross-sectional view through a rapid heating unitpursuant to the present invention having different segmented lamp groupsin the upper and lower banks of lamps;

FIG. 6 a schematic illustration of different arrangement possibilitiesof lamp groups in the upper and lower banks of lamps in a rapid heatingunit;

FIG. 7 a schematic plan view onto a schematic rapid heating unit havingan upper bank of lamps with segmented heating lamps;

FIG. 8 a view similar to FIG. 5, whereby the individual segments of thesegmented lamps in the upper and lower banks of lamps have differentlength ratios;

FIGS. 9 a and 9 b schematic illustrations of heating filaments, ofheating lamps of one group of heating lamps, that are complementary insections;

FIG. 10 is a schematic plan view onto an oven chamber wall having zonesof different reflection characteristics.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 schematically shows the overall construction of a rapid heatingunit 1 for semiconductor wafers 2. The rapid heating unit has an onlyschematically indicated housing 4 (which can also be designated as areactor) that internally defines an oven chamber 6. The inwardly facingwalls of the housing can be coated at least partially in order to form areflector chamber. Provided centrally within the oven chamber 6 is aprocess chamber 8 that is comprised of transparent quartz glass. Withinthe process chamber 8, the wafer 2 that is to be treated is placed uponappropriate support elements 9. The housing 4, as well as the processchamber 8, each have non-illustrated, closable openings for theintroduction and removal of the wafers 2. Furthermore, non-illustratedgas lines are provided for conveying process gases into and out of theprocess chamber 8.

Provided above and below the process chamber 8 are banks of lamps 11,12,which are each formed by a plurality of rod-shaped tungsten halogenlamps 14. Although this is not illustrated in FIG. 1, it is alsopossible to provide banks of lamps or individual tungsten halogen lamps14 to the sides of the process chamber 8. It is, of course, to beunderstood that in place of the rod-shaped tungsten halogen lamps, itwould also be possible to use other lamps.

The wafer that is disposed in the process chamber 8 is heated by theelectromagnetic radiation emitted from the banks of lamps 11,12. Apyrometer 16 is provided for measuring the wafer temperature.

With reference to FIG. 3, a special embodiment of a rapid heating unitpursuant to the present invention will now be described, with thisembodiment in general having the same construction as does thepreviously described rapid heating unit. Therefore, the same or similarelements have the same reference numerals as used in conjunction withthe description of the rapid heating unit of FIGS. 1 and 2.

The rapid heating unit 1 has a housing 4, of which only an upper wall 18and a lower wall 19 are illustrated. The housing 4 forms an oven chamber6 in which is disposed a process chamber 8 comprised of quartz glass.Disposed within the process chamber 8 is a semiconductor wafer 2 that issurrounded by a compensation ring 20 that is disposed on the plane ofthe semiconductor wafer 2. Also indicated in FIG. 3 is a gas inlet oroutlet opening 22 for conveying process gases into or out of the processchamber 8.

Provided above and below the process chamber 8 are banks of lamps 11,12.Disposed in the lower bank of lamps 12 is a plurality of conventionaltungsten halogen lamps 14, only one of which is shown in FIG. 3.

In the upper bank of lamps 11, each two differently segmented lamps24,25 form a lamp group 26, which can also be designated as a multiplelamp. The lamp bulbs or tubes of the lamps 24,25 are secured to commonlamp sockets 28,29. The lamp socket 28, as well as the lamp socket 29,each have a non-illustrated connection by means of which not only thelower but also the upper lamps 24, 25 can be activated. The lamps, withtheir common socket, can be dimensioned such that they can be used inlamp-receiving means of existing rapid heating units, thereby enabling aretrofitting of existing systems. The connection is such that the upperand lower lamps can be activated separately from one another, in otherwords individually and independently of one another. Alternatively, itis, of course, also possible to provide for each of the lamps its ownsocket having its own connection.

The upper lamps 24 are provided with a heating wire or filament 30having a coiled central portion and uncoiled or at least much lesscoiled sections 34. The coiled section 32 is disposed entirely in theregion of the wafer 2. The uncoiled or much less coiled sections 34adjoin the coiled section 32 to the left and to the right, and overlapan edge region of the wafer 2.

The lamp 25 has an uncoiled or not very coiled central section 36, andcoiled edge sections 38. The uncoiled central section 36 of the lamp 25extends over the same range as does the coiled central section 32 of thelamp 24. In the same manner, the coiled edge sections 38 of the lamp 25extend over the same region as do the uncoiled sections 34 of the lamp24.

The coiled and uncoiled sections of the lamps 24 and 25 are thuscomplementary to one another. As a result of different activation of thelamps 24 and 25, it is possible in a straightforward manner to achieve adifferent heating of the central portion of the substrate relative tothe edge portion thereof. During a heating-up phase, for example, thelamp 24 can be activated more pronounced than is the lamp 25, as aresult of which a higher irradiation intensity occurs in the centralportion of the wafer 2 relative to the edge portion thereof.Consequently, the photon-box-effect can be reduced during the heating-upphase. During the controlled cooling-off of the wafer 2, in other words,during the cooling-off accompanied by simultaneous irradiation via thelamps 24,25, the lamp 25 can now be activated more pronounced than isthe lamp 24, as a result of which a greater irradiation intensity occursin the edge portion of the wafer 2 than in the central portion thereof.This reduces a more rapid cooling-off of the edge region and hencereduces the photon-box-effect.

The filaments of the lamps have a constant electrical resistance perunit of length of the filament over the entire filament length, so thatthe coiled regions irradiate with the same intensity at the sameactivation. Alternatively, however, the filaments could also have adifferent electrical resistance per unit of filament length in order toachieve different irradiation intensities. In this way, a wideadaptation of the irradiation characteristics can be achieved.

Although this is not illustrated in FIG. 3, during the thermal treatmentthe wafer 2 can be rotated in the plane of the wafer in order to achievean even more uniform temperature distribution over the surface of thewafer.

FIG. 4 schematically shows an embodiment of an inventive lamp group 40which can be used, for example, in place of the lamp group 26 shown inFIG. 3. The lamp group 40 has an upper lamp 42 as well as a lower lamp43, which are respectively secured at their respective ends to a commonsocket 44, 45. The heating wire or filament 47 of the upper lamp has anuncoiled central section 48, as well as respective coiled edge sections49 adjoining the central section. The upper lamp 42 has a lamp tube 50that is comprised of quartz glass and that, via partitions 51 thatextend transverse to the longitudinal axis of the lamp, forms threechambers 55, 56, 57 that are separated from one another. The length ofthe chambers 55 and 57 centrally corresponds to the length of the coilededge sections 49 and accommodates the same. The middle chamber 56 has alength that essentially corresponds to the length of the central,uncoiled section 48 of the filament 47 and accommodates the same.

A different gas atmosphere (gas composition and/or pressure) is found inthe chambers 55 and 57 than in the chamber 56. If the filament 47 of theupper lamp is activated, this filament, due to the coiled edge regions49, is heated more pronounced in the coiled edge sections 49 than in theuncoiled central section 48. In order nonetheless to provide a stablehalogen process over the entire length of the lamp, there is provided inthe middle chamber 56 a gas atmosphere that enhances a halogen processeven at low temperatures. The gas atmospheres in the respective chambersare adapted to the expected heating of the respective filament sections.

The lower lamp 43 is provided with a heating wire or filament 67 havinga coiled central section 68 and uncoiled edge sections 69 that arecomplementarily disposed relative to the coiled and uncoiled sections49, 48 of the lamp 42. In the same manner as the lamp 42, the lamp 43has a lamp tube 70 that is divided into different chambers 75, 76, 77via partitions 71 that extend transverse to the longitudinal axis of thelamp. The outer chambers 75 and 77 accommodate the uncoiled sections 69of the filament 67, while the middle chamber 76 accommodates the coiledsection 68 of the filament 67. The chambers 75 and 77 again have adifferent gas atmosphere than does the chamber 76.

The separation of the chambers can be effected, for example, by metal,glass or ceramic partitions that are sealed into the lamp tube.Alternatively, however, a tapering of the lamp tube can also effect aseparation of the chambers without additional elements.

FIG. 5 shows an alternative embodiment of a rapid heating unit 1 that isessentially constructed the same as the rapid heating unit 1 of FIG. 3.In contrast to the embodiment of FIG. 3, with the embodiment of FIG. 5also for the lower bank of lamps 12 each two lamps form a group havingcomplementarily arranged coiled and uncoiled sections. Thus, providedabove and below a substrate 2 are banks of lamps 11, 12 that areprovided with complementarily segmented and grouped lamps.

FIG. 6 illustrates different possibilities for arranging the groups thatcomprise two complementarily segmented lamps. With regard to the lampgroups, the circle that contains the cross respectively represents alamp having a centrally coiled section and uncoiled or less greatlycoiled edge sections, whereas the circle having the filled-in pointrepresents a lamp having a non-coiled or slightly coiled central sectionand coiled or more greatly coiled edge sections. The examples I and IIrepresent the presently preferred embodiment of the invention, accordingto which the respective lamps of a lamp group are disposed on a linethat is perpendicular to the plane of the wafer.

However, as illustrated in example III, it is also possible to disposethe respective lamps of a lamp group in a plane that extends parallel tothe plane of the wafer.

The examples IV and V show an arrangement of the respective lamps in aplane that intersects the wafer at an angle of other than 90 degrees.With the examples I, II, III and V, the respective lamps of the lampgroups of the upper and lower bank of lamps are disposed symmetricallyrelatively to the plane of the wafer.

In contrast, example VI shows an arrangement of the lamps of the lampgroup of the upper bank of lamps in a plane that intersects the plane ofthe wafer at an angle other than 90 degrees, whereas the lamps of a lampgroup of the lower bank of lamps are disposed parallel to the plane ofthe wafer.

There thus results different possibilities for arranging the lampswithin the respective lamp groups.

FIG. 7 shows a schematic plan view onto a rapid heating unit 1, wherebythe upper wall of the oven chamber has been removed. The oven chamber isprovided with end walls 80 and 81, as well as with chamber side walls 82and 83 that connect the chamber end walls 80, 81. The chamber end wall80 is provided with an opening for receiving and guiding a gas line 89through that is in communication with a process chamber 88 that isdisposed in the interior of the oven chamber.

Extending between the chamber side walls 82, 83, in at least two planes,are lamp pairs 90 a to q (of which only the upper lamps are illustrated,and which can be disposed, for example, analogously or similarly to thelamp pairs in the bank of lamps 11 in FIG. 3) of an upper bank of lamps91, which will be explained in greater detail subsequently. A furtherbank of lamps can be provided below the process chamber 88, althoughthis is not illustrated in FIG. 7. Provided on the chamber end wall 81is an adapter 95 for a gas discharge system. The gas discharge system inthe adapter 95 is designed such that it enables a laminar gas flowwithin the process chamber 8. There is furthermore provided on thechamber end wall 81 a door for loading and unloading the process chamber88.

Provided in the non-illustrated base and/or in the non-illustrated topwall of the oven chamber is a plurality of gas inlets 96 that aredirected toward the process chamber 88 in order to cool the processchamber by the introduction of a gas.

A semiconductor wafer 97 is accommodated within the process chamber 88and is radially surrounded by a compensation ring 98. The wafer isaccommodated in such a way that it is rotatable about its central axisin the plane of the wafer.

As is illustrated in FIG. 7, the upper plane of the upper bank of lamps91 is provided not only with segmented lamps, i.e. lamps having coiledand uncoiled or less greatly coiled sections of the filament, but alsonon-segmented lamps, i.e. lamps having a generally essentially uniformlycoiled filament. In the segmented lamps, i.e. the lamps 90 a, b, c, d,e, g, k, l, m, n, o, q, the respective central sections of the filamentsare uncoiled or at least not greatly coiled, whereas the respective endsections are coiled. In the second plane of the upper bank of lamps 91,the lamps are inventively embodied to be complimentary to thecorresponding upper lamps. In this way, essentially strip-shaped zones Aand B result having different radiation intensities that are emittedfrom the lamps. In the central zone A there is effected a radiationessentially only via the generally uniformly coiled lamps 90 f, i, j, k,and p, and via the lamps of the second plane of the upper bank of lampsthat are coiled in the central region. In the edge zones B, theirradiation is effected essentially by the lamps that in the edge regioninclude a coiled filament. Overall, the generally uniformly coiled lamps(lamp pairs) 90 f, i, j, k, and p can also be replaced by pairs ofcomplementarily segmented lamps. From the arrangement and the ratio ofthe number of complimentarily segmented pairs and generally coiledlamps, as well as their electrical activation, the zones A and B can bedefined and their magnitude and intensity of irradiation can becontrolled during the process.

As a result of this arrangement of the lamps in combination with therotation of the wafer there result upon the surface of the wafer 97 twodifferent irradiation zones, which are illustrated in FIG. 7 by thedotted line. Within the dotted line, i.e. in a central portion of thewafer, there is effected an irradiation essentially exclusively via thenon-segmented lamps whereas in the region of the wafer disposed beyondthe dotted circle, an irradiation is effected not only by thenon-segmented but also by the segmented lamps, in particular thesegmented lamps 90 g, 90 k and 90 l. By means of suitable individualactivation of the respective lamps it is therefore possible to heat thecentral portion of the wafer 97 differently (and in particular as afunction of the process) from its edge region.

Such a multi-zone irradiation can also be achieved by the use of thelamp groups illustrated in FIGS. 3, 4, 5 and 6, whereby the arrangementof the lamp pairs or groups and/or of their combinations withnon-segmented lamps can be combined in any desired fashion dependingupon requirements. Thus, for example, the lamp pairs described inconjunction with FIG. 7 can be replaced by other groupings, such asthose illustrated in FIG. 6. Furthermore, different groupings are alsopossible within a bank of lamps.

FIG. 8 shows a schematic cross-sectional view of a further embodiment ofa rapid heating unit 1 pursuant to the present invention, which has asimilar construction to the rapid heating unit 1 of FIG. 5. The singledifference lies in a different ratio of the lengths of the coiled anduncoiled sections in the lamp groups of the upper bank of lamps 11 andthe lamp groups of the lower bank of lamps 12. The illustrated sectionallengths are provided in millimeters and are provided for a rapid heatingunit for wafers 2 having a diameter of 200 mm. For the lamp group of theupper bank of lamps 11 the length of the central section is 140 mm,whereas the edge sections respectively have a length of 80 mm. For thelamp group of the lower bank of lamps 12 the central section has alength of 160 mm, whereas the edge sections respectively have a lengthof 70 mm. Due to the different ratios of the sectional lengths thereresult different zones having different irradiation intensities, whichenables an improved heating of the wafer 2 and a reduction of thephoton-box-effect. The indicated lengths of the sections are providedonly as examples and are not limiting. The sectional lengths can beadapted to the respective wafer size and the chamber geometry.

FIGS. 9 a and b show two different embodiments of lamp groups eachhaving two lamps with a lamp filament that is respectively provided withcoiled and uncoiled sections. As can be seen in FIGS. 9 a and b, thecoiled and uncoiled sections of the two lamps of a lamp group are,however, only partially complementary. Thus, pursuant to FIG. 9 a, forexample, with both lamps of the lamp group an edge region havinguncoiled sections of the respective filament are provided. Furthermore,the coiled central section of the lower lamp does not entirely overlapthe uncoiled central section of the upper lamp. At the same time, thecoiled central section of the lower lamp slightly overlaps the rightcoiled section of the upper lamp.

Due to the different arrangement of the coiled and uncoiled regions,different irradiation profiles of the lamp groups can be provided thatcan be adapted to the respective processes and the chamber geometries.

Pursuant to one possible overlapping of coiled or non-coiled sections ofadjacent lamps of a lamp group, this overlapping should be less than 30%of the section length or 10% of the substrate diameter.

FIG. 10 shows a schematic illustration of an upper or lower oven chamberwall of a rapid heating unit 1, which wall is disposed parallel to theplane of the wafer. FIG. 10 shows the inner chamber wall, which, asdescribed previously, can be reflective or coated. The reflectivecharacter is effected, for example, by a coating with gold or adielectric material. In this connection, the inner side of the oven wallhas, however, a central region 100 that has a shape that corresponds tothe projected shape of the wafer that is to be treated. In theillustrated embodiment, a circular shape is provided. Notches or flatsprovided on the wafer are not necessarily taken into consideration forthe design of the central region 100.

The central region 100 is surrounded by an outer region 102. The regions100 and 102 are provided with different reflective characteristics. Inparticular, the central region 100 reflects incident light in a diffusedmanner and/or has a lower reflection coefficient than does the outerregion. There is preferably reflected in the outer region 102 a normal(specular) reflection. In general, the regions can also differ in thespectral nature of their optical characteristics, e.g. in the spectralnature of the refraction index and/or in the reflection coefficients,whereby, for example, a reflection coefficient integrated over aspecific wave length range can be continuously uniform or similar. Thecentral region 100 can, for example, be treated by sandblasting orstreams of abrasive in order to obtain the diffused reflectioncharacteristics. The spectral nature of the optical characteristics canbe influenced, for example, via different coatings of the central andouter regions.

The size of the central region 100 essentially corresponds to the sizeof the substrate that is to be treated, whereby this is again a functionof the dimensions of the process chamber or reactor. If the reflectingand/or refracting surfaces are at a distance of less than 30% from thesurface of the wafer, the central region is between 70% and 130% of thewafer diameter. Included in the selection of the suitable diameter arethe optical characteristics of the wafer, the arrangement of the banksof lamps, and the temperature-time curves of the intended process. Onetries to undertake a selection that is largely independent of the firstand last, whereby the parameters for the central region are then asindicated. It can furthermore be advantageous to provide more than tworegions with different optical characteristics and/or to continuouslyvary the optical characteristics, so that, for example, the reflectioncoefficient of the outer region continuously increases or decreasestoward the outside.

Inner oven walls having regions of different reflectivity lead, duringlonger processes, to a more homogeneous distribution of the temperatureover the surface of the wafer. Even during short, so-called flashprocesses, an improved homogeneity of the distribution of thetemperature of the wafer can be achieved. Furthermore, with units havingsuch modified chamber surfaces, the banks of lamps having conventionalnon-segmented lamps, all of the lamps of a bank of lamps can beactivated with nearly the same electrical power. Up to now, the lampswere differently activated to reduce edge effects. The uniformactivation leads to an increase of the service life of the lamps. Inaddition, with the same electronic power mechanisms, a larger processwindow or a larger control or regulation region is achieved, since allof the lamps can be activated essentially identically. In this way,situations are avoided where a lamp having 40% power is irradiating,while another lamp is irradiating with 80% power, as a result of which amaximum increase of the irradiation capacity, with the irradiationconditions between the lamps remaining the same, results. With a uniformactivation of the lamps, the regulation regions of the lamps can bebetter utilized. This increases the process dynamic and the regulationregion. In this connection, none of the lamps should significantlydiffer upwardly or downwardly from an average value, i.e. the lampcapacities are disposed approximately within a capacity or power windowof about 20% about the average value. A further increase of the processwindow can be achieved by a lower loading of the lamps, if utilized,that are mounted on the side inner walls of the oven. Instead of aloading of nearly 100%, as is normally customary for these lamps, theside lamps are loaded, for example, only to 30% for processes in an oventhat has regions of different reflectivity. If in addition to the ovenregions that are prepared by sandblasting or streams of abrasive, thebanks of lamps are equipped with the inventive lamp groups or multiplelamps, it is possible to still further increase the homogeneity of thetemperature with their help if the irradiation characteristics of theindividual heating bodies, and thus the irradiation field within theoven chamber, are adapted by zones to the process requirements.

In a similar manner, the chamber walls of the process chamber, which iscomprised of quartz, and which chamber walls are disposed parallel tothe plane of the wafer, can also be provided with regions havingdifferent optical characteristics, whereby one region has a projectedshape in conformity with the wafer that is to be treated. The differentoptical characteristics can, for example, include a differentrefraction, especially of the thermal radiation emanating from thewafer, and/or a different absorption magnitude of the thermal radiationemanating from the wafer. In this way, there is avoided that the chamberwall that is disposed parallel to the wafer is locally heated up more inthe region above or below the wafer than are other regions of theprocess chamber, which would reinforce the previously describedphoton-box-effect.

The invention was previously described in detail with the aid ofpreferred embodiments of the invention without being limited to thespecifically illustrated embodiments. The heating unit can, for example,be utilized for RTP-, CVD-, RTCVD-, or epitaxial processes. Thepreviously mentioned features can be combined with one another in anycompatible manner. In particular, the chamber wall having differentreflectivities, or the process chamber wall having different opticalcharacteristics, can be combined with the various lamp forms.

The specification incorporates by reference the disclosure of Germanpriority document 100 51 125.2 filed 16 Oct. 2000 and PCT/EP01/10649filed 14 Sep. 2001.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. An apparatus for thermally treating substrates, comprising: at leasttwo adjacent rod-lamps that extend essentially parallel to one anotherand are each provided with at least one heating filament, each of whichincludes coiled and uncoiled sections, wherein at least parts of said atleast two adjacent rod-lamps are embodied approximately complementary toone another with respect to said coiled and uncoiled sections ofpertaining ones of said filaments, and wherein said rod-lamps have aplurality of chambers that are separated from one another and serve forreceiving different sections of said filaments; and a control device foran individual activation of said filaments of adjacent rod-lamps.
 2. Anapparatus according to claim 1, wherein said filament of one of saidrod-lamps has n coiled sections and m uncoiled sections, while thefilament of an adjacent rod-lamp has m coiled sections and n uncoiledsections, where m and n are respectively integers.
 3. An apparatusaccording to claim 2, wherein said coiled sections of said filament ofone of said rod-lamps are respectively disposed at least partially in aregion of said uncoiled sections of said filament of the adjacentheating element.
 4. An apparatus according to claim 3, wherein saidcoiled or uncoiled sections of said filaments overlap by at most 10% ofa diameter of a substrate that is to be treated.
 5. An apparatusaccording to claim 1, wherein said filaments are symmetrical relative toa plane of symmetry that centrally intersects longitudinal axes of saidfilaments and is disposed perpendicular thereto.
 6. An apparatusaccording to claim 1, wherein respectively at least two adjacent ones ofsaid rod-lamps form a group the rod-lamps of which on at least one sideare associated with one another.
 7. An apparatus according to claim 6,wherein the rod-lamps of a group have a common socket.
 8. An apparatusaccording to claim 1, wherein said filaments respectively have aconstant electrical resistance per unit of length.
 9. An apparatusaccording to claim 1, wherein at least one of said rod-lamps has atleast two chambers for accommodating said filament thereof.
 10. Anapparatus according to claim 9, wherein at least one of a differentpressure and a different gas is provided in at least two of saidchambers.
 11. An apparatus according to claim 1, wherein said filamentof one of said rod-lamps has a centrally disposed coiled section, withadjoining uncoiled sections and wherein said filament of an adjacent oneof said rod-lamps has a corresponding uncoiled central section with twoadjoining coiled sections.
 12. An apparatus according to claim 11,wherein said coiled central section of said one filament has a length ofapproximately ⅘ of a diameter of a substrate that is to be treated. 13.An apparatus according to claim 11, wherein said coiled sections thatare disposed adjacent to a central, uncoiled section have a length ofapproximately ⅓ of a diameter of a substrate that is to be treated. 14.An apparatus according to claim 1, wherein the filaments of saidrod-lamps which deviate from longitudinal axes of said rod-lamps by lessthan 1 mm.
 15. An apparatus for thermally treating substrates,comprising: at least two adjacent rod-lamps that extend essentiallyparallel to one another and are each provided with at least one heatingfilament, each of which includes coiled and uncoiled sections, whereinat least parts of said at least two adjacent rod-lamps are embodiedapproximately complementary to one another with respect to said coiledand uncoiled sections of pertaining ones of said filaments, and acontrol device for an individual activation of said filaments ofadjacent rod-lamps, wherein an oven chamber is provided that surroundssaid rod-lamps and is provided, for a radiation of said rod-lamps, withreflective inner walls, wherein one inner wall that is disposedapproximately parallel to a plane of a substrate that is to be treatedis provided with at least two zones having different reflectioncharacteristics, and wherein at least one of said zones correspondsessentially to a projected shape of said substrate.
 16. An apparatusaccording to claim 15, wherein said at least one zone reflects lightthat is incident therein in an essentially diffused manner.
 17. Anapparatus according to claim 15, wherein at least one zone of said innerwall is blasted with abrasive.
 18. An apparatus according to claim 15,wherein one other zone has a shape that differs from said projectedshape of said substrate.
 19. An apparatus according to claim 15, whereinsaid at least one zone corresponds essentially to a size of saidsubstrate.
 20. An apparatus for thermally treating substrates,comprising: at least two adjacent rod-lamps that extend essentiallyparallel to one another and are each provided with at least one heatingfilament, each of which includes coiled and uncoiled sections, whereinat least parts of said at least two adjacent rod-lamps are embodiedapproximately complementary to one another with respect to said coiledand uncoiled sections of pertaining ones of said filaments, and acontrol device for an individual activation of said filaments ofadjacent rod-lamps, wherein a process chamber is provided foraccommodating a substrate that is to be treated, wherein said processchamber has walls that are disposed between said rod-lamps and saidsubstrate and that are essentially transparent for a radiation of saidrod-lamps, wherein a wall of said process chamber that is disposedessentially parallel to a plane of a substrate that is to be treated isprovided with at least two zones having different opticalcharacteristics, and wherein one of said zones corresponds essentiallyto a projected shape of said substrate.
 21. An apparatus according toclaim 20, wherein said one zone is essentially transparent for thermalradiation emitted from said substrate.
 22. An apparatus according toclaim 20, wherein said one wall of said process chamber has a shape thatdiffers from said projected shape of said substrate.
 23. An apparatusaccording to claim 20, wherein said one zone corresponds essentially toa size of said substrate.
 24. An apparatus for thermally treatingsubstrates, comprising: a housing that forms an oven chamber; at leastone source of radiation disposed within said oven chamber; and a processchamber disposed in said housing for accommodating a substrate that isto be treated, wherein said process chamber is essentially transparentfor radiation of said source of radiation, wherein at least one wall ofsaid process chamber that is disposed essentially parallel to a plane ofsaid substrate that is to be treated is provided with at least two zoneshaving different optical properties, and wherein one of said zonesessentially corresponds to a projected shape of said substrate.
 25. Anapparatus according to claim 24, wherein said rod-lamps have a pluralityof chambers that are separated from one another and serve for receivingdifferent sections of said filaments.
 26. An apparatus according toclaim 24, wherein said one zone is essentially transparent for thermalradiation emitted from said substrate.
 27. An apparatus according toclaim 24, wherein said one wall of said process chamber has a shape thatdiffers from said projected shape of said substrate.
 28. An apparatusaccording to claim 24, wherein said one zone corresponds essentially toa size of said substrate.
 29. An apparatus for thermally treatingsubstrates, comprising: at least two adjacent rod-lamps that extendessentially parallel to one another and are each provided with at leastone heating filament, each of which includes coiled and uncoiledsections, wherein at least parts of said at least two adjacent rod-lampsare embodied approximately complementary to one another with respect tosaid coiled and uncoiled sections of pertaining ones of said filaments,and a control device for an individual activation of said filaments ofadjacent rod-lamps, wherein said parallel-extending rod-lamps overlaythe substrate parallel to a chord of a circle defined by the center ofthe substrate with each extent of the substrate along the chord beingcollectively overlade by a complementary pair of a coiled heatingfilament section of one rod-lamp and an uncoiled heating filamentsection of the other rod-lamp, and said control device individuallyactivates said filaments of said rod-lamps such that, during a firstperiod of the thermal treatment of the substrate, the coiled heatingfilaments of the one rod-lamp are activated to provide irradiationintensities that are more pronounced than the contemporaneousirradiation intensities of the other rod-lamp and, during a subsequentperiod of the thermal treatment of the substrate, the coiled heatingfilaments of the other rod-lamp are activated to provide irradiationintensities that are more pronounced than the contemporaneousirradiation intensities of the one rod-lamp, whereupon each extent ofthe substrate that is overlade by one of said complementary pairs ofcoiled and uncoiled heating filament sections is subjected to adifferent irradiation intensity during the first period of the thermaltreatment of the substrate than during the subsequent period of thethermal treatment of the substrate.
 30. An apparatus according to claim24, further comprising: at least two adjacent rod-lamps that extendessentially parallel to one another and are each provided with at leastone heating filament, each of which includes coiled and uncoiledsections, wherein at least parts of said at least two adjacent rod-lampsare embodied approximately complementary to one another with respect tosaid coiled and uncoiled sections of pertaining ones of said filaments,and a control device for an individual activation of said filaments ofadjacent rod-lamps.
 31. An apparatus according to claim 25, wherein atleast one of a different pressure and a different gas is provided in atleast two of said chambers.